The water the storms bring quickly flows off the landscape into streets and rivers, with much of the remnant moisture evaporating in the summer sun. The monsoon is driven by the sun heating up the land and the Pacific Ocean at different rates, with land surfaces warming more quickly than the ocean.
The warm land creates low-pressure zones as hot air rises. Once this pattern establishes across the region, the winds shift to fill in the vacuum. With this shift in the winds, the monsoon begins in northern Mexico in May. The moisture-laden monsoon air travels north to Arizona and New Mexico, encouraged by the pressure difference between the hot, parched southwestern air and the cooler Mexican air. Southwest monsoon season in Arizona, although the thunderstorms that bring the rain may form in different times and places across the region.
In addition to being variable in space, some years produce weak monsoons, while others provide ample rain. There are no evident trends in annual monsoon strength, making it difficult to predict. The result? The Arizona Monsoon is a well-defined meteorological event technically called a meteorological 'singularity' that occurs during the summer throughout the southwest portion of North America. During the winter time, the primary wind flow in Arizona is from the west or northwest—from California and Nevada.
As we move into the summer, the winds shift to a southerly or southeasterly direction. Moisture streams northward from the Pacific Ocean and the Gulf of Mexico. This shift produces a radical change in moisture conditions statewide. Such a change, together with daytime heating, is the key to the Arizona monsoon.
This wind shift is the result of two meteorological changes:. These two features combine to create strong southerly flow over Arizona. The southerly winds push moisture north-ward from Mexico. The exact source region for the moisture of the Arizona monsoon is unknown. By the way, the term "monsoons" as in "when the monsoons arrive There is no such beast. The word should be used in the same manner that "summer" is used.
Consequently, the proper terminology is "monsoon thunderstorms" not "monsoons. Monsoon thunderstorms are convective in nature.
By that, we mean that the thunderstorms are powered by intense surface heating. In addition, strong moisture influx into Arizona is also required.
It originally was linked to the total amount of water in the atmosphere above the weather station a precipitable water amount of 1", a quantity thought to be necessary for convective thunderstorm activity. Temperatures needed to produce Tucson's thunderstorms are somewhat lower. The Arizona monsoonal circulation does not produce thunderstorms every day during the months of July-September but rather occurs in a pattern that has "Bursts" and "Breaks".
According to climatologist Andrew Carleton:. In lower levels, during a "burst", there is strong surface heating and strong southerly or southeasterly transport of moisture into Arizona. This creates intense atmospheric destabilization and leads to strong widespread thunderstorm outbreaks. Our own meteorologists suggest that a break usually occurs when the subtropical ridge re-develops over NW Mexico and drier air spreads into Arizona. The first phase is a series of spotter training sessions presented by National Weather Service personnel and members of the Office of Climatology at Arizona State University.
Specific training is given in observing and evaluating visually unique or distinct atmospheric phenomena in the Southwest United States such as dust walls, dust devils, and eddies or vortices associated with down bursts Caracena et al. Much of this training complements existing severe storm spotter programs such as the Arizona Skywarn Amateur Radio Network. The spotter training uses the materials and follows the type of instruction suggested by the National Weather Service Moller Storm cells in Arizona are generally short-lived.
There are three basic stages of thunderstorm development: the updraft cumulus stage, the mature stage and the dissipating stage. The lifecycle of a thunderstorm cell going through these stages is, on average, about minutes. The first stage of thunderstorm development is the updraft cumulus stage. In this stage, the primary activity within the cell is pronounced vertical uplift. Warm moist air is lifted adiabatically and condenses to form cumulus-type cloud formations.
As the updraft stage continues, the formation of towering cumulus begins. Torrential thunderstorms may be experienced, especially over the mountains, and are occasionally enhanced by the passage of tropical waves.
Flash flooding is common during the Arizona monsoon, as dry washes can instantly turn into flowing rivers. As a result, tourists are advised not to camp in the dry wash during monsoon season. Rainfall is not continuous but varies considerably depending on a number of factors. There is usually a period of sustained rainfall and a period of relief from the rain. In the Sierra Madre Occidental , rainfall can reach between 10 and 15 inches.
Rain during the monsoon is capable of reversing the downward draw from reservoirs, and farmers also depend on the rains for their crops and livestock feed. In addition to rainfall and thunderstorms, the Arizona monsoon also causes lightning, dust storms, strong winds, and sometimes dangerous fires. Monsoon thunderstorm over the Arizona desert.
Sophy Owuor May 28 in Environment.
0コメント